Semiconductor chip detects environmental parameters

Materials World magazine

,

1 Dec 2007

A semiconductor chip whose surface can sense parameters such as temperature, humidity, light and certain gases is being developed by wireless sensor manufacturers ChipSensors Ltd, based in Limerick, Ireland.

The company has applied porous polymers and silicon oxides to the surface of a complementary metal oxide semiconductor chip. These dielectric materials, commonly used in sub-micron chips, can selectively admit or block agents.

‘It is like a sponge,’ says Tim Cummins, CEO of ChipSensors. ‘Moisture, humidity and gases can get into the pores, and because of the high specific surface area, you get changes in the dielectric constant, which we can measure with [18-bit] converters.

Cummins, who previously worked at the Westinghouse Electric Corporation in Dublin, Ireland, as a designer of electronics for sensors, became aware of the porous oxides commonly used in humidity and gas sensors several years ago. In the past seven years, he says, silicon chip companies have begun replacing traditional silicon dioxides with porous silicon dioxides, but only to reduce capacitance and make the chips go faster.

Cummins and his associates soon realised that the porous materials could also provide chips with a sensory function. They set up ChipSensors in 2006 to pursue this technology.

‘We’re not trying to re-invent the wheel or come up with an exotic new material. What we are doing is piggy-backing on other semiconductor technologies,’ he says.

The company demonstrated a 0.13µm chip prototype at the RFID Europe 2007 exhibition in September, and is hoping to release a commercial product in 2008. As well as humidity, light and temperature, the surface of the device can detect light flammable gases, such as ethanol and toluene, and some chlorofluorocarbon refrigerant gases, which can be measured at room temperature.

Cummins envisages the chip being used in building monitoring and air conditioning, as well as in food and pharmaceutical packaging. ‘The chips contain a non-volatile memory and radio transmitter, making them ideal for measuring the temperature of perishable products every five to 10 minutes,’ he says.

Professor Christopher Snowden, Vice Chancellor of the University of Surrey, UK, and a specialist in semiconductor materials, says ‘This sounds relatively novel and interesting. One of the problems with porous sensors is the gradual degradation in the material – but I know there have been improvements.’

ChipSensors’ researchers are developing products to detect gases at temperatures of 200ºC, and are working with other research institutes to introduce antibodies to the chips to detect bacteria such as listeria and E.coli. They are also hoping to produce a wireless version in 2008.